Technical Field
-
The present invention relates to a method for controlling a valid date
for data in a distributed processing system in which plural computers are
connected by communication circuits, a computer-readable media recording
a program that realized this method, and an apparatus for controlling the
valid date for the data.
Background Art
〈〈Section 1: Data access in distributed processing system〉〉
〈〈Section 1.1: Introduction of plural copies〉〉
-
Frequent access from many computers to an original data existing
only in one computer within the distributed processing system, in which
plural computers are connected by communication circuits, leads increase
and concentration in communication quantity [Problem 1] . It would lead
further problems such as deterioration in a system response. In order to
solve the problem without introducing an enormous communication
equipment, the inventor of this invention has proposed a method in which
"user's computers (clients) generate, hold, and utilize their own copies of an
original data received from a computer holding the original data (server)".
This method eases the absolute quantity and the concentration in
communications. Despite of this merit, the method accompanies a
possibility of causing the increase in communication quantity as a server
tries to notify a revision in its original data simultaneously towards its
plural clients without delay [Problem 2].
〈〈Section 1.2: Assignment of valid date for copy by client〉〉
-
Thereby, Japanese patent application HEISEI6-215031 (Document 1)
illustrates an idea for permitting uncertainty in a coincidence of an original
data and its copy (Line 45-47 of sixth column in Document 1). In specific,
clients assign an expiration date for a date that has already been determined
on the copy (Line 30-32 of seventh column in Document 1), and assume that
the copy is valid till the expiration date (Line 1-2 of seventh column in
Document 1). In Patent 2504218 (Document 2), clients generate a renewal
expected time by adding a certain period of time to a renewal time (Line
36-37 of sixth column in Document 2) on the assumption that an original
data is to be renewed for every certain periods (Line 30-35 of sixth column in
Document 2).
-
In both methods described in the above, it is the clients that assume
(of their own accords?) the valid date for data.
〈〈Section 1.3: Assignment of valid date for copy by server〉〉
-
On the contrary, there is a method in which a server assigns and
distributes a valid date for copy as it distributes a content of an original data
to its client. If the client can confirm in usage that the copy is valid by
referring to the valid date, it would not need to access to the server. If it
finds the copy invalid, it would receive the latest original data by accessing to
the server and generate a new copy.' If an original data can be renewed
within the server in correspondence with the valid date determined in
advance, the server would be enabled to distribute the latest data with the
minimum communication quantity at 'all the time. PCT/JP97/00971
(Document 3) illustrates this technical idea.
〈〈Section 1.4: Problems in valid date revision〉〉
-
A new problem would arise, however, when an original data of a
server is revised at an unexpected time. Its concrete example is a revision
in a valid date for an original data (Abc.html) from June 26 to May 20 (FIG1).
An original data before May 20 is Version 1, and an original data after May
20 is Version 2. A client holding a copy of Version 1 is unable to recognize a
revision in the original data until the first valid date (June 26) so it would be
continuously utilizing the old data [Problem 3].
-
In order to solve this problem, Document 2 suggests a method for a
server to send its all clients (client computer) the renewed data, the renewal
time, and the renewal expected time when the original data is unexpectedly
renewed (Line 1-2 of second column and Line 3-4 of seventh column in
Document 2). If a number of clients is many, the server needs to make a lot
of communications for the notification. As a result, it would cause
[Problem 2] . Therefore, the method described in the above is effective
only if the amount of necessary communication equipment can be calculated
from the maximum of the number of clients as well as the investment for the
communication equipment is tolerable.
-
Document 1 does not illustrate any processes accompanying the
unexpected renewal in original data. This is due to its concept determined
by adopting the idea for permitting uncertainty in coincidence of the original
data and its copy and by assuming a system usage considering this
uncertainty (Paragraph 10 in Document 2). This is a solution method
limited to the distributed processing system exclusively used for a specified
business that is capable of designing a program action and a system usage
form of both the server and the client all together.
〈〈Section 2: Application to web data and problems thereof〉〉
-
An original of web data (data) opened to clients on a server by
Internet and Intranet is also only one and is accessed by many clients.
Therefore, it also has the same problems described in the previous section.
-
It is not applicable to adopt the idea for permitting uncertainty in
coincidence of the original and its copy as Document 1 on Internet to which
many and unspecified operators participate. In reality, clients who cannot
permit uncertainty frequently access to the server and cause [Problem 1],
as indifferent clients cause [Problem 3] .
-
The method in Document 2 has [Problem 2] . A realization of this
method on Internet which requires "the server to hold a list of clients that
have referred to the specified web data (data) and hold own copies of the web
data" would accompany many difficulties in technical field [Problem 4] .
Moreover, it is technically difficult for a server to send renewed data to its
clients without delay because the general clients using dial-up circuits do not
make connections with Internet at all the time [Problem 5] .
-
Although the method in Document 3 in which "the server assigns the
valid date for every web data (data) and notifies it to its clients, and the
clients utilize its own copies only if they are valid" solves [Problem 1] and
[Problem 2], it accompanies [Problem 3] for unexpected revision in
original data. In reality, it is often difficult to appropriately determine the
valid date for web data in advance. There are data like the weather forecast
that are regularly renewed for certain period of time. However, most of
renewal plans for the web data cannot be determined in advance. A system,
for example, that makes a revision in a web data after finding a description
mistake can be considered indifferent to a necessity for renewal before it
finds out the mistake.
-
[Problem 1] , [Problem 2] , and [Problem 3] held originally by
the distributed processing system are mutually related; when one problem
is reduced, another problems would increase. Although it is difficult to
solve these problems perfectly, the present invention tries to clarify a method
for reducing these problems simultaneously and greatly as well as solving
[Problem 4] and [Problem 5] that arise on Internet etc.
DISCLOSURE OF THE INVENTION
〈〈Section 3: Basic mechanisms〉〉
〈〈Section 3.1: Notification of valid date revision〉〉
-
"A procedure for inspecting a valid date for a copy when accessing to
the copy of data recorded within a client and determining to utilize the copy
if it is valid or to obtain the latest original data from the server if it is not
valid", that is "a mechanism for obtaining the original data only if the data is
, and the data is necessary" is already disclosed by the inventor of this
invention in Document 3. To combine' a mechanism for "notifying the
clients of only a revision in valid date" with the mechanism described above
is the basic device (Device A) in this invention. It enables the realization of
an effective data renewal with the synergism of both mechanisms. It
simultaneously solves
Problem 1 to
Problem 5 through its mechanism for
"notifying the clients only a revision in valid date". Followings are further
devices for the solution (B1 to B9).
〈〈Section 3.2: Complexity in condition control led by notification of only
revision in valid date〉〉
-
It is not easy to notify a revision in valid date appropriately to clients
in need of this notification. One of its reasons is because clients with a
various conditions exist on Internet or Intranet. FIG1 explains it with an
example.
-
In FIG1, (Version 1 of) Abc.html, an original data, is set up in a
server on May 5 with its (first) valid date set on June 26. Abc.html is later
renewed with a new content (Version 2) on May 20, and its valid date is
renewed to July 10 as well.
-
On the one hand, clients accessing to the server on and after May 20
and requesting Abc.html a new would receive the content of Version 2 with
its valid date (July 10). On the other hand, clients holding Version 1 with
its first valid date (June 26) would receive a notification of new valid date
(May 20) by a process described in later sections (Section 3.4 to 3.6).
Because this notification of revision is carried out according to various
circumstances of every clients, there is no guarantee to finish notifying
revisions to all clients within a certain period of time. As a result, there
would be clients with a various conditions.
-
Followings are explanations for the various conditions of clients as
described in order of periods grouped in certain period of time.
[Before May 5]
-
- (A) a client without holding a copy of Abc.html
exists only.
-
[May 5 to May 20]
-
- (A) a client without holding a copy of Abc.html,
- (B) a client recording a copy of Version 1 of Abc.html and its first valid date
(June 26),
exist all together. The client accessing to the copy of Version 1 in Condition
(B) confirms that the copy is valid and utilizes it as the latest data without
accessing to the server.
-
[May 20 to June 26]
-
- (A) a client without holding a copy of Abc.html,
- (B) a client recording a copy of Version 1 of Abc.html and its first valid date
(June 26),
- (C) a client recording a copy of Version 1 of Abc.html and its new valid date
(May 20),
- (D)a client recording a copy of Version 2 of Abc.html and its first valid date
(July 10),
exist all together. The client in Condition (B) shifts into Condition (C) when
receiving a notification of the new valid date for Version 1 from the server.
The client in Condition (C) shifts into Condition (D) by accessing to the
server when detecting the copy of Version 1 as expired in its access. The
client in Condition (A) shifts into Condition (D) by accessing to the server
when Abc.html is necessary. If the client in Condition (B) is not notified of
the new valid date for Version 1, the valid date for Version 1 the client holds
stays as the first valid date of June 26 as it is. It means that the client
cannot detect in its access that the copy is expired. The client, therefore,
does not make access to the server and thus, continue to be in Condition (B).
This condition produces [Problem 3] . Methods for this case will be
explained in Section 3.4 to 3.6. The client accessing to Version 2 in
Condition (D) utilize the copy of Version 2 as the latest data without
accessing to the server because the copy is valid.
-
[June 26 to July 10]
-
There are Condition (A), (B), (C), and (D). The clients accessing to Version 1
in Condition (B) and (C) shift into Condition (D) by accessing to the server
and receiving Version 2 with its valid date of July 10 when it detect the copy
as expired in its access to Version 1. The client accessing to Version 2 in
Condition (D) utilizes the copy of Version 2 as the latest data without
accessing to the server because the copy is valid.
[On and after July 10]
-
There is still a possibility for Condition (A), (B), (C), and (D) to be exist. The
clients accessing to Version 1 or Version 2 in Condition (B), (C), or (D) shift
into Condition (A) by accessing to the server when detecting the copy as
expired, and detecting the absence of the effective original data. The point of
time at which all clients shift into Condition (A) is also the point of time at
which all clients finish accessing to the copy of Abc.html. It suggests that
this point of time is unpredictable.
-
In real usage, the system revises the valid date of Version 1 to May
20 when (such as May 18) it determines a plan for renewing the valid date of
Version 2 of Abc.html to May 20. Moreover, it carries out further revision in
Abc.html and renewal in its valid date as well as revision in other data or its
valid date. Therefore, conditions in the reality are much more complicated.
〈〈Section 3.3: Effects of notifying clients of renewed valid date〉〉
-
Notifying the clients only the valid date (May 20) that has been
renewed from an old version (such as Version 1) brings greater effect.
Because this notification makes the valid date reliable, the clients would be
enabled to utilize the copy within itself with "guarantee as the latest data"
(or "by assuming it as the latest data with high reliance"). In other words, it
greatly reduces [Problem 1] as it controls unnecessary communication with
the server. This is one of the effects of Device A.
-
Even with this method, renewed original data (Version 2) would be
necessary for clients and would be transferred anyhow. In other words, the
method does not solve Problem 2 perfectly, but it would save Version 2 from
being sent to all the clients. Only the clients in need of data which detect
the copy as expired in its access make access to the renewed original data
within the server. Although data such as an encyclopedia including many
items might have corrections in misprint or rewritten items based on new
discovery, users who look through all those renewed items must be very rare.
Therefore, when adopting the method in this invention by setting up the
valid date for every items in an encyclopedia CD-ROM, the server would only
send the renewal contents of items that are necessary for its users. This
would greatly reduce communication quantity (compared to the method in
which the server sends all revision contents). It is almost unthinkable for
any users to look through all the renewed data (except for a very particular
case). The quantity of data to be sent to users would be reduced as a case,
in which end-users do not make access to renewed data or the data is further
renewed before the end-users make access to it, occurs more frequently
(effect of Device A).
-
Moreover, in Method A of this invention, the only case in which the
clients access to the server for obtaining the latest original data would occur
when the clients access to the copy of data existing within itself and detect
that the copy is expired. This would reduce the concentration of
communications compared to the method in Document 2 in which the server
sends the renewed original data simultaneously towards many clients.
-
As described in above, Method A of this invention accompanies much
lesser communication load compared to [Problem 2] which occurs when the
server simultaneously notifies its clients of a whole revised data as described
in Document 2. Besides, it continues to hold its advantage for which the
clients can obtain the latest data when necessary (effect of Device A).
〈〈Section 3.4: Various methods for notifying clients of renewed valid date〉〉
-
There are several methods for notifying new valid date to computers
holding a copy of a version when a valid date of an original data of the
version is renewed. One of the methods is to simultaneously notify only the
revised valid date. It would accompany much lesser communication
quantity compared to the method described in Document 2, in which a server
simultaneously notifies the whole renewed data. This would greatly
improve the condition in [Problem 2] . There is also a method for notifying
a revision in valid date by E-mail. This method solves [Problem 5] as well.
A program attached to E-mail revises a corresponding valid date recorded
inside a client.
-
Following is a method that further reduces the communication
quantity, distributes a concentration of communications, and solves
[Problem 4] and [Problem 5] .
〈〈Section 3.5: Method for effectively notifying clients of renewed valid
date〉〉
-
The method solves [Problem 4] and [Problem 5] by referring to
a server from end-user computers (Device B1). This is a polling (reference)
from clients towards the server.
-
In order to reduce [Problem 1] by far, the method makes a further
device on timing for polling utilized for receiving a notification of revision in
valid date. If a schedule for a client to poll its server of a revision in valid
date is set at 3 o'clock in (every) morning, the conventional method has been
making the client to communicate by establishing a connection towards
Internet only at this designated time. If the client fails to make
communication, it would wait for a next scheduled time. Therein, this
invention enables the client to make communication as soon as it
successfully establishes the connection towards Internet (for other purpose)
after the designated time (3 o'clock in morning) (Device B2). If it fails to
establish the connection towards Internet at the designated 3 o'clock in
morning, it would not make any communication then and would only register
for piggyback communication for the next time it makes communication (for
other purpose). Therefore, this method solves a problem that "an user is
required to pay for unexpected cost of communication made by an automatic
system for making connection towards Internet by dial-up at midnight". If,
for example, an operator accesses (checks E-mail etc.) to Internet by utilizing
this computer (client) at 9 in morning, it would simultaneously start the
polling towards a server, in other words, it refers (to the server) a revision in
valid date. The server notifies the revision in valid date at this point in
time, and thereby, [Problem 3] could be solved. In other words, a client
shifts from Condition (B) of <May 20 to June 26> in Section 3.2 into
Condition (C). If a client makes access to a copy of Version 1 before
accessing to Internet, it would continue to be in Condition (B), and therefore,
[Problem 3] could not be solved. However in reality, a spread of Internet
has made users to make frequent access to Internet, and thus, it has reduced
situations for [Problem 3] to occur. This method avoids the situation
described in Method 2 in which clients receive unexpected full-body data that
has been renewed. It (the method in this invention) rather let the clients
receive only the data of unexpectedly revised valid date on a communication
which the clients make for some necessities, in other words, the clients
receive data by a piggyback process. In this system, a number of
communications appears to be fixed for the clients, and an increase in
communication quantity stays small. [Problem 2] is solved through this
system of the method. A number of clients who notice the piggyback
communication described above can be considered to be small.
-
A device for further reducing a communication quantity and a
number of receptions of revised valid date is the mechanism (Device B3) for
collectively receiving plural revised data on valid dates. Clients collectively
receive the plural revised data on valid dates from their server as they
connect to Internet by dial-up circuit. It is "collective notification of valid
dates" for the server. It accompanies much less quantity and time of
communication compared to the method in which clients check revisions in
valid date for every files of each web data (effect of Device B3).
-
There is a further necessity for a device (Device B8) for saving clients
from receiving another one of same revised data of valid date which they
have already received in beforehand. Its details will be explained in Section
3.6.3.
〈〈Section 3.6: Condition control corresponding to the method for notifying
only revision in valid date〉〉
-
Section 3.2 has explained that there are various conditions of clients.
The followings are concrete methods for controlling these conditions.
〈〈Section 3.6.1: Procedure for generating first copy and recording valid
date〉〉
-
When generating a first copy of a data (such as Abc.html) within a
client, the system records [designation of original data, version distinguish
data, valid date] in correspondence with the copy (Device B4). Followings
are details for each one of them. A set of this data will be called as "control
label" in the rest of the text.
- (1) Designation of original data:
It is the data indicating a place where the original data that has been
the origin for a copy exists. URL without the designation of communication
protocol (and the designation of port) indicates a place on Internet where the
original data exists.
- (2) Version distinguish data:
There is a possibility for the original data to be revised over and over
again. A data designating specific contents (data) among those revised
original data is the version distinguish data. Version number is its concrete
example. The first original data is Version 1, and it transforms into Version
2, Version 3, and so on, according to following revisions.In the conventional method represented by Document 2, a server
notifies all clients of a content of the latest original data (such as Version 2)
and its valid date (such as July 10) so that it had been unnecessary for the
clients to be aware of versions of data. In the method of this invention,
however, the server revises valid date of copy of old content (data) existing
within clients so that it becomes necessary for the clients to clarify the
version of the copy.
- (3) Valid date:
It is the valid date of data of designated version.Clients, the requester of the data, previously understand the
designation of original data (URL) among the data described in the above.
The rest of the data, the version distinguish data and the valid date ([Version
1, June 26] for the period before May 20 in FIG1), would be notified to the
clients from the server. The clients record these sets as the control labels.
-
〈〈Section 3.6.2: Contents of notification of revision in valid date and
process of clients thereof〉〉
-
As a server revises a valid date of a data, it notifies its clients of
[designation of original data, revised version, revised valid date] in return
to polling made by the clients. In other words, the server sends a revised
control label. The clients that receive the notification would rewrite the
corresponding "control label" for "designation of original data" and "version
data" (they actually rewrite the valid date).
-
If a client has a copy of data of a version older than the designated
version, and its valid date is set longer than the notified valid date, it would
rewrite the existing valid date with the notified valid date (Device B5). This
idea is based on a hypothesis that the valid date of the copy of old version
must be no longer than that of new version. In this case, a point in time for
generating or revising the version can be used as a data for distinguishing
the version instead of version number (Device B6).
〈〈Section 3.6.3: Introduction of control label list and previous reception
time〉〉
-
A server collectively distributes plural revised data of valid dates (that
is the revised control labels) in return to the polling made by its clients
(Device B3). It is useless, however, to send same contents at every time.
Therein, the following method (Device B7) introducing "previous reception
time" is effective.
-
The server lines up revised control labels 202 in order of their revised
time. It then matches records (of the server) of listing time 203 with each
one of those control labels. FIG2 illustrates this system.
-
If there are no designations of time in polling made by the clients, the
server notifies the clients of the all control labels on the list as well as the
server time at which the notification is made. This is the "previous
reception time". The clients hold this time and notify it to the server at the
next polling. The server, on return, notifies the clients of only the control
labels added to the list after the time notified by the clients as well as the
server time at which the notification is made. In this way, the
communication quantity can be reduced as the server sends only the control
labels added to the list after the previous reception time (effect of Device B7).
〈〈Section 3.6.4: Notification of control target for valid date within client〉〉
-
If a client, in its polling, notifies its server of the designation of
original data of which the client controls the valid date (Device B8), the
server would be able to notify the client of only the revised data of the valid
date of this original data (that is the revised control label). This device
would further reduce the communication quantity (effect of Device B8).
-
However, a quantity of data of which a client notifies its server would
be predictably high as a number of the control labels the client holds
increases. For example, suppose the designation of original data that is
control target for valid date has been designated by URL, a client with 200
control labels must notify its server of the 200 URL for ever polling.
-
In order to solve this problem, all original data existing under a
directory path of a URL are determined as the control target for valid date
(Device B9). In other words, collecting a bunch of original data as a set of
original data of control target for valid date under one URL enables clients to
notify the server of only one URL. This one URL is called "top designation
of control target original data". The server notifies its clients of a revision
in original data existing under the top designation of original control data
(notified by the clients). This device reduces the communication quantity as
it enables the client to notify the server of only one URL (top designation of
original control data) instead of the 200 URL described in the previous
example (Effect of Device B9).
BEST MODE OF OPERATING THE INVENTION
〈〈Section 4: Computers connected by communication networks〉〉
-
FIG3 illustrates computers related to this invention and Internet 301
connecting these computers. There are "data server" 303 holding original
data and "client" 302 reading the original data. A server sending
homepages is the data server 303, and many computers such as personal
computers reading these homepages are the clients 302.
-
Besides them, there is "control server" 305 that controls valid date
data of data existing within the data server and sends revised data of the
valid date to its clients. It is possible to combine tasks of data server 303
and control server 305 into one computer. However, if plural data servers
303 hold original data that is control target for valid date, control server 305
that is common to those data servers should be utilized for the convenience.
It enables the client 302 to obtain valid date revised data only by polling to
this one (or small number of) common control server 305.
-
There is "input/output computer to control server" 304. It controls
setting or revision of valid date of original data held by data server 303 and
notifies control server 305 of the revision in valid date. The input/output
computer to control server 304 can be realized as one with client 302 or data
server 303 or control server 305.
-
Followings are details of valid date control within client 302 and
control server 305.
〈〈Section 5: Client〉〉
〈〈Section 5.1: Hardware construction of client〉〉
-
FIG4 illustrates a construction of hardware of a client. The
hardware operates "process at web data reception", "process for retrieving
web data requested by operator", and "polling process towards server".
These processes can also be operated by a general computer (such as
personal computer) equipped with communication functions.
-
Followings are details of these processes and relationships with the
hardware construction illustrated in FIG4.
〈〈Section 5.2: Process at web data reception〉〉
-
FIG5 illustrates the process at web data reception. This process is
started when there are no valid copies of web data inside client computers in
the process for retrieving web data (Section 5.3). Within the client
apparatus, input analysis unit 411 analyzes a signal from input unit, and the
signal would be sent to "web data control unit" 410 if it is the request for web
data. If there are valid copy in recording unit for web data 405 within
recording unit 403, it would be displayed on display unit 412. If there are
non, the apparatus would start communication control unit 402, connect to
Internet 401, and receive web data from data server 303. A copy of this web
data would be recorded on recording unit for copy 406 of recording unit for
web data 405 and would be displayed on display unit 412.
-
In the series of processes, processes operated just at the web data
reception are started with a process for "receiving web data, version data,
valid date from data server 303" 501. If a received web data is HTML file, it
would check if the top designation of original control data is included in the
text. This is "search for top designation of original control data" 503. It
first searches if a series of letters "AlwaysNew" exists in a comment within
the HTML file. One following the series of letters is the top designation of
original control data.
-
If <!AlwaysNew:www.atele.com/> has been written on the file,
"www.atele.com/" would be the top designation of original control data. It
implies that the valid dates of all web data included in this path (included in
the directory or sub-directory) are controlled by the method of this invention.
-
If there is the top designation of original control data, the system
would record it in "recording unit for top designation of original control data"
415. This is the step to "register top designation of original control data"
505. This record would be unnecessary if the same record already exists.
Next, it "attaches "control target mark" to copy of recorded web data" 510.
This control target mark would be utilized in a process for retrieving web
data (Section 5.3).
-
If there are no top designations of original control data in the
received HTML file, it judges if URL of the received web data is included in
the top designation of original control data recorded in "recording unit for top
designation of original control data" 416. This is the series of the processes
starting with the step to "sequentially retrieve top designations of original
control data" 506, passing through a judgment of "finish?" 507 and the step
to "judge if URL of received web data is included in retrieved top designation
of original control data" 508, and ending with a judgment of "included?" 509.
-
If a data is considered as the control target, the system "attaches
"control target mark" to copy of recorded web data" 510. It then "generates
and records (in recording unit for control label 407) control label referring to
version data and valid date" 511 of received web data.
〈〈Section 5.3: Process for retrieving web data〉〉
-
FIG6 illustrates the process for retrieving and providing web data
requested by operators (or programs) of clients. Within the clients'
apparatus, input analysis unit 411 analyzes the operators' requests that
have been input into input unit 413. If they are considered as the requests
for web data, a signal would be sent to "web data control unit" 410. At this
time, the system first "obtains URL of requested web data" 601, and then it
searches for a copy of the requested web data by accessing to recording unit
for copy 406.
-
If it cannot find any copies, it would notify the signal to
communication control unit 402 and "receive the latest web data from data
server 303, copy and record it" 610 by connecting to Internet 401. Its details
are already explained in Section 5.2. The system finally "provides copy of
web data to requester" 611.
-
If the system finds the copy of requested web data in recording unit
for copy 406, it would "judge if control target mark is attached" 604 to the
copy. The control target mark would be set up in the process at web data
reception described in Section 5.2.
-
If the control target mark is not attached to the copy, the system
would operate the following processes just the same as a normal web data.
It first "confirms general validity of copy" 608. A general browser offers
selection of ways for confirming new version of pages that have been saved as
setting of "Internet temporary file" as following: "confirm every time
operator displays pages", "confirm every time operator starts the browser",
and "do not confirm". The system of this invention also adopts the above
selection and confirms the validity of copy referred to it in the step to
"confirm general validity of copy" 608. If the copy is considered invalid, it
would "receive the latest web data from data server 303, copy and record it"
610 and then "provide copy of web data to requester" 611. If the copy is
considered valid, it would just "provide copy of web data to requester" 611.
-
If the control target mark is attached to the copy, the system would
search for corresponding control label from "recording unit for control label"
407 and "judges if valid date (recorded on it) is not yet expired" 606. If it is
considered valid, the system would just "provide copy of web data to
requester" 611. If it is considered invalid, it would "receive the latest web
data from data server 303, copy and record it" 610, and then it would
"provide copy of web data to requester" 611.
-
In the procedure described in the above, if the control target mark is
not attached to the copy, clients would utilize their own copy of web data or
request original data a new, etc. based on the standard which operators of
the clients have designated (irrelevant to intentions of data distributor).
Contrary, if the control target mark is attached to the copy, the clients would
operate process on the assumption that the valid date which has been
originally assigned by data distributor and has been recorded on control
label is correct. This is due to the fact that the clients previously assume
"revision in valid date to be notified when it happens".
〈〈Section 5.4: Polling process towards server〉〉
-
FIG7 illustrates the polling process towards control servers. After
connecting to the control server, clients would "send top designation of
original control data" 711 to their server. The top designations of original
control data are (in many cases) plural and are recorded in recording unit for
top designation of original control data 415. The communication control
unit 402 notifies the contents to the control server through Internet 401.
-
Next, the clients "send record of previous reception time". The
"previous reception time" has been notified by the control server to the
clients in "process for receiving polling from client" explained in Section 6.3
and has been recorded by the clients. The clients notify it to the control
server.
-
The control server transacts the above data (according to the
procedure in Section 6.3) and selects "revised control label" that should be
sent to the clients. Then, the clients "receive (plural) revised control
label(s)" 713.
-
The clients sequentially retrieve the received control label and
operate the following process. They first "specify record of control label
holding designation of original data equivalent to that of received control
label (from recording unit for control label 407)" 716. If there is the record,
they would then "judge if (version of) specified control label is equivalent to
or older than version distinguish data of received control label" 718. If they
are equivalent in the version, the clients would "rewrite valid date of
specified control label with valid date of received control label" 722.
-
If the version of the specified control label is older than that of the
received control label, the clients would "judge if valid date of specified
control label will be expired later valid date of received control label" 720. If
it is considered to be expired later, the clients would "rewrite valid date of
specified record of control label with valid date of received control label" 722.
〈〈Section 5.5: Process for starting polling process towards server〉〉
-
The polling process towards server has been explained in Section 5.4.
FIG8 illustrates the procedure for starting this process. A polling schedule
is input from input unit 413, is analyzed in input analysis unit 411, and is
notified to renewal schedule control unit 409. Although the polling
schedule is recorded in recording unit 403 in real usage, FIG4 omits this
description. The renewal schedule control unit 409 checks the polling
schedule recorded in recording unit 403 at a breaking in from timer 414. If
it is just at the time for operating polling, the system would operate "process
at the time when polling towards control server is planned" described in
FIG8 (a).
-
Herein, the clients first "confirm connection towards Internet" 801.
If it has been already connected, they would "start polling process towards
control server (explained in Section 5.4)" 804. If it has not been connected
yet, they would register the process to be started later as the connection
towards Internet is established for other purpose. This is the process to
"register polling process towards control server as post-connection process (to
registering unit for piggyback process 404)" 803.
-
When general processes such as browser or E-mail are started after
input from input unit 413 has been analyzed in input analysis unit 411,
"general processing unit" 408 operating these processes sends signal to
communication control unit 402, and the connection towards Internet is set
up. At this time, clients start the process following the connection towards
Internet described in FIG8 (b). The clients first "retrieve process registered
as post-connection process" 805 by accessing to registering unit for piggyback
process 404. If there is "polling process towards control server" registered
by a step to "register polling process towards control server as
post-connection process (to registering unit for piggyback process 404)" 803
described in FIG8 (a), the clients would'operate the process described in
FIG7.
〈〈Section 6: Control server〉〉
〈〈Section 6.1: Hardware construction of control server〉〉
-
FIG9 illustrates the construction of hardware of control server 305.
"Process for receiving revised control label" and "process for receiving polling
from client" are operated on this hardware. These processes can also be
operated by general computers (such as personal computer) equipped with
communication functions. Followings are explanations for details of these
processes with reference to the hardware construction in FIG9.
〈〈Section 6.2: Process for receiving revised control label〉〉
-
FIG10 illustrates the process for receiving revised control label.
"Communication control unit" 902 corresponds to the access from
input/output computer to control server 304 towards control server 305 and
sets up a path between them. The input/output computer to control server
304 sends the revised control label, and "reception unit for revised control
label" 903 receives it. This process is "reception of revised control label"
1001 described in FIG10.
-
The clients "search if control label equivalent to designation of
original data of received control label and its version distinguish data exists
on control label list" 1002. The control label list of which the construction
has been already explained with FIG2 is recorded on recording unit for
control label list 906. Although FIG2 describes the control labels sent from
input/output computer to control server 304 towards control server 305 as
"revised control label list", they are simply called as "control label list" here
since they are all revised control labels.
-
The clients would delete corresponding control labels if there are any.
This is the process for "deleting corresponding control label existing on
control label list" 1003. After they finish this process or as soon as they
determine that there are no corresponding control labels, the clients "add
received control label to the end of control label list" 1004. Then, they
"record time (of this point in time) of control server on this control label"
1005.
〈〈Section 6.3: Process for receiving polling from client〉〉
-
FIG11 illustrates the process for receiving polling from client 302.
The client 302 accesses to control server 305 when the polling process
towards server (Section 5.4) has been started within client 302.
"Communication control unit" 902 corresponds to this access and sets up a
path between the client 302 and control server 305. A signal is sent to
"reception unit for polling from client" 904 though the path. Followings are
descriptions for this process.
-
Clients first "put mark on the top of control label list 201" 1101 and
then "receive previous reception time" 1102. If there are no previous
reception time, they would shift into processes on and after C. If there are
previous reception time, they would "compare time of control server recorded
on control label (within control label list that has been recorded in recording
unit for control label list 906) with received previous reception time" 1105,
find the oldest control label among those newer than the received "previous
reception time", "transfer mark to this control label" 1107, and shift into
processes on and after C explained in the following.
-
In the processes on and after C, the clients first "receive top
designation of original control data" 1108. This top designation of original
control data could be plural. The clients "judge if designation of original
data of marked control label is included in received top designation of
original control data" 1111 by sequentially transferring the mark towards
newer control labels. If it is considered included, a server would "send
contents of (marked) control label to client" 1113. Through the processes
described in the above, the server sends client 302 the (revised) control labels
that are included in the received top designation of original control data and
exist on and after the previous reception time. The server finally "sends the
present time of control server to client" 1114.
INDUSTRIAL APPLICALILITY
-
Frequent access from many computers to an original data existing
only in one computer within the distributed processing system, in which
plural computers are connected by communication circuits, leads increase
and concentration in communication quantity ( [Problem 1] [Problem 2] ).
Thereupon, the method for making plural users' computers (clients) to hold
copies of the original data had been proposed (Document 1, Document 2) as
its solution. However, a collective notification of revision in the original
data towards the plural users' computers rather had made another increase
and concentration in the communication quantity. Thereupon, the
inventor of this invention has proposed the mechanism in which a data
provider assigns the valid date to the copy of original data and a client
generates and utilizes the copy of the latest original data by accessing to its
server when detecting in its access that the copy of original data is invalid
(Document 3). However, this method has still accompanied the problem
( [Problem 3]) as it cannot handle the unexpected revision in original data of
server.
-
Internet and Intranet also have the problems described in the above
as well as problems such as "it is difficult for the server to hold a list of
clients holding copies of web data by referring to the specified web data
(data)( [Problem 4])" and "it is difficult to send renewed data to clients using
dial-up circuits without delay ( [Problem 5] )".
-
In order to solve these problems, this invention has proposed the
procedure for "notifying the clients of only the revision in valid date" in
addition to the procedure for "inspecting the validity of a copy when
accessing to the copy of data recorded within a client and determining to
utilize the copy if it is valid or to obtain the latest original data from the
server if it is not valid" (Device A). In specific, the system "records control
label (designation of original data, version distinguish data, valid date) when
generating a copy of original data within a client" (Device B4) and controls
the valid date by utilizing this control label.
-
The notification of revision in valid date makes the valid date recorded
within the clients reliable. The clients would make communication with
server only when they discover in access that the copy of data has been
expired. As a result, operators of the client computers are provided with
their necessary data in the latest form, and at the same time, the absolute
quantity and concentration of communication quantity are greatly eased.
-
The communication quantity can be further reduced by "operating
polling referring the renewal in valid date from end-user computer towards
server" (Device B1), "operating the polling as soon as clients successfully
establish the connection towards Internet (for other purpose) after the
designated time" (Device B2), "collectively receiving plural revised data on
valid dates" (Device B3), "notifying server of the time for receiving revised
data at the next polling" (Device B7), "notifying server of the designation of
original data of which the clients control the valid date at the polling (Device
B8), "determining all original data existing under the top designation of
original control target data as the valid date control target (Device B9).
